Jackson Mapper returning null with spring rest

Question

I am getting Json from this link

I am using following two pojo classes for mapping .

1)NewsSource.class

@JsonIgnoreProperties(ignoreUnknown = true)
@JsonInclude(JsonInclude.Include.NON_NULL)
@JsonPropertyOrder({ "status", "sources" })
public class NewsSource {

    @JsonProperty("status")
    private String status;
    @JsonProperty("sources")
    private List<Source> sources = null;

    @JsonProperty("status")
    public String getStatus() {
        return status;
    }

    @JsonProperty("status")
    public void setStatus(String status) {
        this.status = status;
    }

    @JsonProperty("sources")
    public List<Source> getSources() {
        return sources;
    }

    @JsonProperty("sources")
    public void setSources(List<Source> sources) {
        this.sources = sources;
    }

}

2)Source.class

    @JsonIgnoreProperties(ignoreUnknown = true)
    @JsonInclude(JsonInclude.Include.NON_NULL)
    @JsonPropertyOrder({ "id", "name", "description", "url", "category", "language", "country", "sortBysAvailable" })

    public class Source {

        @JsonProperty("id")
        private String id;
        @JsonProperty("name")
        private String name;
        @JsonProperty("description")
        private String description;
        @JsonProperty("url")
        private String url;
        @JsonProperty("category")
        private String category;
        @JsonProperty("language")
        private String language;
        @JsonProperty("country")
        private String country;
        @JsonProperty("sortBysAvailable")
        private List<String> sortBysAvailable = null;
//getter setters generated with IDE , and annotated with @JsonProperty too

I'm using this code to mapping json to pojo .

 public NewsSource getNewsSource() {
        String URL = source_url; //above mentioned url to get json
ObjectMapper omapper= new ObjectMapper();
        omapper.setVisibilityChecker(omapper.getSerializationConfig().getDefaultVisibilityChecker()
                .withFieldVisibility(JsonAutoDetect.Visibility.ANY)
                .withGetterVisibility(JsonAutoDetect.Visibility.NONE)
                .withSetterVisibility(JsonAutoDetect.Visibility.NONE)
                .withCreatorVisibility(JsonAutoDetect.Visibility.NONE));

   NewsSource newsSource =null;
        try {
        String result = restTemplate.getForObject(URL, String.class);
//result is returnning data properly
            omapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
            newsSource = omapper.readValue(result, NewsSource.class);
//newsSource returnning null
}catch (Exception ex){

System.out.println("oooh exception ");
}

I have tried many suggested tricks that are mentioned on this link but no one worked for me :)

Note: I am using following maven dependency for Jackson .

        <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
    </dependency>

Any suggestion would be appreciated. thanks in advance

Update I have used following code .

    private static Object getJsonObject(String str) {
        Object obj = null;
        try {
            ObjectMapper mapper = new ObjectMapper();
            mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
            if (str != null) {
                obj = mapper.readValue(str, NewsSource.class);

            }
        } catch (Exception exc) {
            exc.printStackTrace();
        }
        System.out.println("json obj:===>" + obj);
        return obj;
    }

    public NewsSource getNewsSource() {
        String URL = source_url;

        NewsSource newsSource =null;
        try {
            String result = restTemplate.getForObject(URL, String.class);
            //String jsonStr=getJsonString(result);
            ObjectMapper mapper = new ObjectMapper();
        //    newsSource = mapper.readValue(result, NewsSource.class);

            newsSource= (NewsSource) getJsonObject(result);
            System.out.println("done:" +newsSource);
}catch (Exception ex){

System.out.println("oooh exception ");
}

        return newsSource;
    }

StackTrace

    com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.util.ArrayList out of VALUE_STRING token
 at [Source: {"status":"ok","sources":[{"id":"abc-news-au","name":"ABC News (AU)","description":"Australia's most trusted source of local, national and world news. Comprehensive, independent, in-depth analysis, the latest business, sport, weather and more.","url":"http://www.abc.net.au/news","category":"general","language":"en","country":"au","urlsToLogos":{"small":"","medium":"","large":""},"sortBysAvailable":"top"},{"id":"al-jazeera-english","name":"Al Jazeera English","description":"News, analysis from the Middle East and worldwide, multimedia and interactives, opinions, documentaries, podcasts, long reads and broadcast schedule.","url":"http://www.aljazeera.com","category":"general","language":"en","country":"us","urlsToLogos":{"small":"","medium":"","large":""},"sortBysAvailable":"top"},{"id":"ars-technica","name":"Ars Technica","description":"The PC enthusiast's resource. Power users and the tools they love, without computing religion.","url":"http://arstechnica.com","category":"technology","language":"en","country":"us","urlsToLogos":{"small":"","medium":"","large":""},"sortBysAvailable":"top"},{"id":"associated-press","name":"Associated Press","description":"The AP delivers in-depth coverage on the international, politics, lifestyle, business, and entertainment news.","url":"https://apnews.com/","category":"general","language":"en","country":"us","urlsToLogos":{"small":"","medium":"","large":""},"sortBysAvailable":"top"},{"id":"bbc-news","name":"BBC News","description":"Use BBC News for up-to-the-minute news, breaking news, video, audio and feature stories. BBC News provides trusted World and UK news as well as local and regional perspectives. Also entertainment, business, science, technology and health news.","url":"http://www.bbc.co.uk/news","category":"general","language":"en","country":"gb","urlsToLogos":{"small":"","medium":"","large":""},"sortBysAvailable":"top"},{"id":"bbc-sport","name":"BBC Sport","description":"The home of BBC Sport online. Includes live sports coverage, breaking news, results, video, audio and analysis on Football, F1, Cricket, Rugby Union, Rugby League, Golf, Tennis and all the main world sports, plus major events such as the Olympic Games.","url":"http://www.bbc.co.uk/sport","category":"sport","language":"en","country":"gb","urlsToLogos":{"small":"","medium":"","large":""},"sortBysAvailable":"top"},{"id":"time","name":"Time","description":"Breaking news and analysis from TIME.com. Politics, world news, photos, video, tech reviews, health, science and entertainment news.","url":"http://time.com","category":"general","language":"en","country":"us","urlsToLogos":{"small":"","medium":"","large":""},"sortBysAvailable":"top"},{"id":"usa-today","name":"USA Today","description":"Get the latest national, international, and political news at USATODAY.com.","url":"http://www.usatoday.com/news","category":"general","language":"en","country":"us","urlsToLogos":{"small":"","medium":"","large":""},"sortBysAvailable":"top"}]}; line: 1, column: 402] (through reference chain: com.example.demo.dto.NewsSource["sources"]->java.util.ArrayList[0]->com.example.demo.dto.Source["sortBysAvailable"])
    at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:270)
    at com.fasterxml.jackson.databind.DeserializationContext.reportMappingException(DeserializationContext.java:1234)
    at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1122)
    at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1075)
    at com.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.handleNonArray(StringCollectionDeserializer.java:260)
    at com.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.deserialize(StringCollectionDeserializer.java:187)
    at com.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.deserialize(StringCollectionDeserializer.java:177)
    at com.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.deserialize(StringCollectionDeserializer.java:20)
    at com.fasterxml.jackson.databind.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:504)
    at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:104)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:276)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:140)
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:287)
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:259)
    at com.fasterxml.jackson.databind.deser.std.CollectionDeserializer.deserialize(CollectionDeserializer.java:26)
    at com.fasterxml.jackson.databind.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:504)
    at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:104)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.vanillaDeserialize(BeanDeserializer.java:276)
    at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:140)
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3814)
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2858)
    at com.example.demo.Utill.RuleUtill.getJsonObject(RuleUtill.java:80)
    at com.example.demo.Utill.RuleUtill.getNewsSource(RuleUtill.java:100)
    at com.example.demo.Service.NewsApiService.getSource(NewsApiService.java:32)
    at com.example.demo.Controller.Home.somespecific(Home.java:56)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:108)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:478)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
    at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803)
    at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1459)
    at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)
json obj:===>null
done:null

just null pointer exception , because exception occurred at mapping . — naila naseem, Nov 18 '17 at 03:54

score 1 · Accepted Answer · answered Nov 20 '17 at 03:04

I modified your source code as follows due to some reasons:

RestTemplete will automatically convert the response Json string into specified POJO as you defined in NewsSource and Source.
As I said above, the method getJsonObject is redundant.
Your exception handling in the method getNewsSource didn't print the true cause.

getNewsSource

public NewsSource getNewsSource() {
    String URL = source_url;

    NewsSource newsSource =null;
    try {
        /*
        String result = restTemplate.getForObject(URL, String.class);
        ObjectMapper mapper = new ObjectMapper();

        newsSource= (NewsSource) getJsonObject(result);
        System.out.println("done:" +newsSource);
        */

        newsSource = restTemplate.getForObject(URL, NewsSource.class);
        System.out.println("done:" + newsSource.toString());
    } catch (Exception ex){
        System.out.println("oooh exception \n" + ex);
    }

    return newsSource;
}

Hope this helps you! :)

o great . its worked . so getForObject does everything , no need of mapper .Good — naila naseem, Nov 20 '17 at 03:27
Yes, you got it! Spring framework provides many APIs to reduce our effort while coding. — LHCHIN, Nov 20 '17 at 06:21

score 0 · Answer 2 · answered Nov 17 '17 at 14:40

The code is working correctly. Looks like you are using older version of jackson. I tested with 2.9.0 and below code is working as expected although with 2.9.0 version setVisibilityChecker(.....) is deprecated.

public static void main(String[] args) {

    NewsSource nSource=new NewsSource();

    nSource.setStatus("status");

    Source source=new Source();

    source.setCategory("category");

    List<Source> sList=new ArrayList<Source>();
    sList.add(source);

    nSource.setSources(sList);

    String jsonStr=getJsonString(nSource);
    //{"status":"status","sources":[{"category":"category"}]}
    System.out.println(jsonStr);

    NewsSource newsSource =(NewsSource)getJsonObject(jsonStr);
    //NewsSource@1810399e
    System.out.println(newsSource);

}

private static String getJsonString(Object object) {
    String jsonString = "";
    try {
        ObjectMapper mapper = new ObjectMapper();
        if (object != null) {
            jsonString = mapper.writeValueAsString(object);
        }
    } catch (Exception exc) {
        exc.printStackTrace();
    }
    System.out.println("jsonString:===>" + jsonString);
    return jsonString;
}

private static Object getJsonObject(String str) {
    Object obj = null;
    try {
        ObjectMapper mapper = new ObjectMapper();
        mapper.setVisibilityChecker(mapper.getSerializationConfig().getDefaultVisibilityChecker()
                .withFieldVisibility(JsonAutoDetect.Visibility.ANY)
                .withGetterVisibility(JsonAutoDetect.Visibility.NONE)
                .withSetterVisibility(JsonAutoDetect.Visibility.NONE)
                .withCreatorVisibility(JsonAutoDetect.Visibility.NONE));

        mapper.disable(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES);
        if (str != null) {
             obj = mapper.readValue(str, NewsSource.class);

        }
    } catch (Exception exc) {
        exc.printStackTrace();
    }
    System.out.println("json obj:===>" + obj);
    return obj;
}

com.fasterxml.jackson.core jackson-annotations 2.8.0 com.fasterxml.jackson.core jackson-core 2.8.7 com.fasterxml.jackson.core jackson-databind 2.8.0 compile — Har Krishan, Nov 18 '17 at 05:27
Do not use any other dependency except 3 mentioned above and try to create the json the way I created using the Jackson and then deserialize the object from generated json string. It should work. If that will be the case then may be the problem with the json string that you created. — Har Krishan, Nov 18 '17 at 05:32

Jackson Mapper returning null with spring rest

2 Answers2